They join rivals including the Nokia Download Store, Motorola's film site, built by Saffron Digital, with yet another rumoured to be en route from Microsoft.

Each is simple, slick and well stocked, but sadly completely siloed from others. There is a danger the market will stall as consumers become confused by the wealth of walled garden options as the market matures.

Finally this week digital music retailers have decided to promote a universally recognised 'MP3-compatible' logo in a bid to drive sales of the DRM-free format. The music industry is keen to offer consumers confusion-free convenience (nma.co.uk 04.11.08).

Of course it would be much simpler if an MP3-style standard existed on mobile allowing developers to write one app for every phone. That's not happening soon due to the ongoing differences between rival phone manufacturers' platforms, screen sizes and individual handset power so each legitimately pursues solo stores.

And these stores have helped solve discoverability and usage issues which have traditionally plagued the apps market. But as time goes on a walled garden sales approach could be damaging as consumers, who switch phones and simply don't know where to go next. Equally a more open market encourages browsing and downloading.

A question remains as to whether separate stores will aggravate consumer confusion or a convenient one-stop shop service will eventually prevail.